Predefined-time Attitude Tracking Control for Liquid-filled Spacecraft Under Angular Velocity and Torque Constraints

This paper addresses the attitude tracking control problem of liquid-filled spacecraft in the presence of angular velocity constraints and limited control torque. Significant challenges arise in spacecraft attitude control due to the increased nonlinearity and uncertainty in spacecraft dynamics resulting from large-amplitude liquid fuel slosh during attitude tracking missions. Firstly, the sloshing liquid in partially-filled tanks carried by the spacecraft is described by the Moving Pulsating Ball Model, and the interaction torque between rigid body and pulsating ball is equivalent to the internal disturbance. Secondly, a predefined-time disturbance observer is introduced to estimate the internal and external disturbance. After that, two sliding mode variables are designed to ensure that the angular velocity can track the desired value within a predefined time and satisfy the constraints. Furthermore, a predefined-time sliding mode attitude tracking controller is proposed, and a predefined-time auxiliary subsystem is proposed to deal with the torque constraint. Finally, the effectiveness of the proposed control algorithm is verified by numerical simulation.